This invention relates to gas-liquid contact apparatus, and it particularly pertains to novel crossflow trays for use in fractionation towers and other apparatus.
In a typical crossflow tray installation, a number of horizontal tray with openings therein are mounted in a sealed, vertically elongated vessel known in the industry as a column or tower. Each trays is formed of a plurality of panels, and the margin areas of the panels overlap each other and are bolted together. The only openings in the overlapping areas are holes which receive the panel-connecting bolts. Liquid is introduced on the upper surface of the uppermost tray. At the downstream end of each tray, there is a weir which leads to a downcomer; and, the downcomer leads to an unperforated upstream area (the "downcomer seal area") on the next lower tray. Gas is introduced into the lower end of the tower. As the liquid flows across the trays, gas ascends through the openings in the trays and into the liquid to create bubble areas where there is intimate and active contact between the gas and liquid. In the margin area where adjacent panels overlap, there are no openings for ascending vapors. In towers used in high liquid rate systems such as light hydrocarbon distillations and direct contact heat exchange, each tray level may have multiple sets of flow paths including a downcomer, bubbling area and downcomer seal transition area.
Many crossflow trays are simple sieve trays, i.e. decks which have hundreds of circular holes. Some trays have valves associated with the tray openings, and others have fixed deflectors. In an example of the latter, shown and described in U.S. Pat. No. 3,463,346 of Aug. 26, 1969, each tray opening includes a trapezoidal aperture in the plane of the tray deck, and a stationary deflector which overlies and is aligned with the aperture. The deflector and the adjacent deck surface define lateral outlet slots which are oriented to direct vapor which passes up through the aperture in directions which are generally transverse to the flow direction of liquid on the deck.